Thermal injury has been shown to suppress many aspects of both specific and nonspecific immune responses. We investigated the effect of two histamine H-2 antagonist drugs on cell-mediated immunity in burned mice, utilizing a method of quantitating the degree of contact sensitivity elicited to the antigen, 2,4-dinitrofluorobenzene (DNFB). Following sensitization by painting the abdomen with DNFB, animals were challenged 5 days later by painting the ears; subsequent ear swelling is a sensitive and reproducible measure of cell-mediated immunity. We have previously demonstrated that burned mice are maximally immunosuppressed 10 to 14 days following burn injury. In the present study we found that daily intraperitoneal administration of appropriate doses of the H-2 antagonists cimetidine (2 and 10 mg/kg/day) and ranitidine (2 and 10 mg/kg/day) resulted in maintenance of normal cell-mediated immunity in burned animals. Neither a lower dose of ranitidine (0.2 mg/kg/day) nor higher doses of cimetidine (20 and 50 mg/kg/day) restored immunity, and diphenhydramine, an H-1 antagonist, had no effect. There was no augmentation of contact sensitivity in unburned mice treated with cimetidine. The immunorestorative effect is probably secondary to antagonism of histamine H-2 receptors on suppressor T lymphocytes, and may reflect increased suppressor cell activity in burned mice; however, other mechanisms may be involved.
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